Screen unit for ball mills



J. SEROY July 19, 1938.

Filed Sept. 29, 1934 2 Sheets-Sheet l w R N m m m b 0 m. R x 3 Q V mm NN INVENTOR W y m m .J

July 19, 1938. J. SEROY 2,124,127

SCREEN UNIT FOR BALL MILLS Filed Sept. 29, 1934 2 Sheets-Sheet 2INVENTOR JOIZJZ/ Seroy I ATTQRNEY Patented July 19, 1938 UNITED STATESPATENT OFFEE SCREEN UNIT FOR BALL MILLS John Seroy, Stockton, Calif.

Application September 29, 1934, Serial No. 746,157

2 Claims.

This invention relates to mining machinery and is directed particularlyto an ore grinding or pulverizing mill of that character commonly knownas ball mills or cannon ball mills.

One of the objects of my invention is to provide means within the ballmill whereby all exceedingly hard and non-grindable material may beaccumulated and retained from continued contact between the steel ballsand the raceways.

Small exceedingly hard chips of steel from broken drills etc. often aredischarged with the ore through the hopper into the ball mill. If thesechips are allowed to remain in the raceways of the mill more than a fewminutes they will seri- 15. ously damage the face of the raceways andprobably in time damage the steel balls.

A further object of my inventionis to provide a ball mill wherein theore is subjected to successive grinding and pulverizing actions. Thesesuccessive actions upon the ore assure that it will be completely brokendown into fine particles prior to passage over the amalgam plate andprovides for a very effective grinding action within a compact space.

'. It is also my object to provide a sectional screen about the mill andthrough which the fine material passes. This screen is constructed as asectional unit for. the reasons as will hereinafter appear.

As an additional object it is my purpose to pro- Vide an automaticcontrol within the ore hopper of the ball mill in order that the flow ofcrushed ore into the hopper may be automatically controlled according tothe volume of ore being ground within the mill.

A further object of the invention is to produce a simple and inexpensivedevice and yet one which will be exceedingly effective for the purposefor which it is designed.

These objects I accomplish by means of such structure and relativearrangement of parts as will fully appear by a perusal of the followingspecification and claims.

In the drawings similar characters of reference indicate correspondingparts in the several views:

Figure 1 is a sectional elevation of my improved ball mill.

Figure 2 is a top plan of the same partly broken out, and

Figure 3 is a fragmentary enlarged plan view of the screen andsupporting members.

Referring now more particularly to the characters of reference on thedrawings, the numeral 55. denotes a circular base plate of heavycast'metal provided with an integral and downwardly depending supportingfiange 2. This base plate i is formed with concentric outer and innerand vertically offset grooves 3 and 4 forming raceways. These racewaysare properly machined 5 and tempered in order to prevent undue wear.

Intermediate the adjacent raceways 3 and 4 is formed an upstandingportion 5 so that the top periphery of the plate outwardly of the outerrace is on a level lower than said portion 5. The 10 faces of thisportion 5 are a continuation of the surfaces of said raceways which arerelatively deep.

Formed on the opposite side surfaces of the inner raceway 4 are endlessrelatively small 15 grooves 6 and 6a. These concentric grooves 5 and 6aare of course depressed in the base plate I and are for the purposehereinafter described.

A cone 1 is formed centrally of the base plate the cone also beingconcentric with the raceways 20 3 and 4 and grooves 6 and 6a. The uppersurface of the cone is tangent to the adjacent side of the raceway 4;the groove 6a being disposed adjacent the junction of the cone with theraceway.

Supported in the raceways are steel balls B, 25 said balls beingsomewhat smaller in diameter than that of the raceways. The raceway 3 ispreferably provided with eleven balls, and the raceway 4 with six ballswhich do not fill the respective raceways, as indicated in Figure 2. 3

Supported on the balls B and in frictional engagement therewith is acircular head 8 also of heavy cast material. This upper head member 8 isformed with relatively shallow raceways 9 and I 0. These raceways 9 andID are concentric and are formed in cooperating alinement with the lowerraceways 3 and 4 respectively.

The interior surface of the head 3 extends downward some distance on theouter side of the raceway II] as at I! to a termination adjacent 4d thehorizontal axial plane of the corresponding balls in order to provide arelatively narrow passage I2 between the concentric raceways.

The head 8 is provided with a central opening l3 into which the neck ofa downwardly converg- 45'- ing ore feeding hopper I4, is secured bysuitable means.

Secured to the periphery of the head 8 is an upstanding drum I5. Thisdrum I5 serves as the drive pulley which may be driven as by a belt 50-I6. Mounted adjacent the periphery of the head 8 and engaging the lowerportion of the drum I 5 is a circumferential splash preventing flangeIT. This flange as well as the drum is secured to the head by bolts l8.

A sectional screen unit indicated generally at I9 surrounds the head 8in spaced relation theretothe lower edge of said screen unit beingsupported in a peripheral recess 20 about the top of the base plate Iand extending upward therefrom at an acute angle.

' This sectional screen unit I9 comprises adjacent screen sections ZIsecured in place as follows:

An upper and inner band 22 circumferentially continuous is supported inspaced relation from the drum I by means of upstanding arms 23 set attheir lower end in the recess 20 and extending up to connect with theband 22 at an acute angle. The above structure constitutes the innerframe work against the outer face of which the screen sections 2I areheld in place by means of a lower and outer band 24 and an upper andouter band 25. These latter bands 24 and 25 are formed in semi-circularsections with ears e formed on the ends thereof-each pair of sectionsbeing adjustably secured together by bolts and thumb screws 26 joiningthe adjacent pairs of ears. The lower band 24 of course rests againstthe plate at the bottom of the recess 20 while the upper band 25 is heldin place by fingers 21 which engage the upper and inner band 22 asshown. The screen sections 2| are overlapped along adjacent longitudinaledges in the direction of rotation of the head 8 as shown in section inFigure 3.

Surrounding the base plate I and extending out from flanged engagementtherewith is an amalgamating plate 28 which is set on a slight slope.This amalgamating plate 28 is formed with a fluid retaining flange 29and an outlet spillway 30 along the lower edge.

In use my improved ball mill operates as follows:

The ore is fed into the hopper I4 along with the necessary amount ofwater and passes through the neck of the hopper onto the cone I fromwhence it flows evenly into the inner raceway 4.

The head 8 is rotated relatively slow by the belt I6 driving about thepulley I5. As this exceedingly heavy head 8 rotates the steel balls Brotate as well as travel around the raceways 3 and 4. The ore enteringthe mill is initially ground in the inner raceway and due to the narrowoverflow passage I2 no large pieces of ore can escape without beingcrushed. Any particles of hard non-grindable material such as pieces ofsteel drills entering the mill with the ore are at once forced away fromthe balls B into the deep grooves 6 and 6a where they remain withoutharm to the mill until it is cleaned. Also, due to the position of thegroove 6a it will catch some of such pieces as they slide down theraceway before they reach the same.

After passing through the inner gangue it passes over the raised portion5 into the outer raceway 3 where it is subjected to further and morethorough grinding action.

Passing from the outer raceway the gangue flows through the screen unitI9 either by centrifugal force or by gravity. The screens retain all orewhich by chance escapes the mill in any substantial size and alsoretains any foreign matter incapable of passing through the screen. TheV-shaped annular groove formed between the plate I and the lower screenband 24 serves as a catch trough for any amalgam which may have passedthrough the mill.

After flowing through the screen the gangue runs over the initialamalgamating plate 28 and thereafter passes through the spillway 30 fora further amalgamating process.

If, during the operation of my ball mill, one of the screens is damaged,it is only necessary to untighten the thumb screws 26 which in turnloosen the retaining bands 24 and 25. The damaged screen section is thenreadily removed and replaced by a new screen section. The new screensection overlaps the adjacent screen section in the direction ofrotation of the head 8 and is lapped under the other adjacent screensection. The sections are thus lapped in order that the fiow of ganguewill not run against a raw edge of the screen.

As the mill is operated and the ore flows through the hopper I4 into themill, the head 8 will gradually rise up relative to the base plate I dueto the congestion of ore therebetween. I make use of this movement inpreventing too great congestion within the mill in the following manner:

Mounted within the hopper I4 adjacent the top edge thereof is acircumferentially tapered cam 3I. An upwardly tapering roller tappet 32is formed on the lower end of the ore feed control rod 33said tappet 32being adapted to cooperate with the cam 3I.

This rod is part of any well known feed control device, such forinstance as that shown in Patent No. 879,581 granted February 18, 1908to F. B. Pettingill; the oscillating roll-supporting pendent yoke 29 ofthe patented structure corresponding of course to the rod 33.

Thus, as the mill is operated, the feed control roll is actuated only atregular intervals due to the roller tappet 32 contacting and riding upthe cam 3|. An intermittent ore feed is thereby provided.

If however the intermittent feed supplies too great a quantity of ore tothe mill the head 8 will raise vertically, causing the roller tappet toonly partially engage the cam or to fail to engage the cam entirely,resulting in the feed being greatly reduced or entirely stoppedrespectively. This result is obtained due to the action that as the head8 raises vertically, the cam within the hopper also is raised and as theroller tappet is tapered upwardly the cam in the raised portion willonly partially move the feed control or may not even move it at all. Asthe mill empties the head 8 of course lowers. and the cam again engagesthe tappet and the intermittent feed again functions.

By forming the cam within the hopper rather than on the outside of thedrum I5, as is common practice, the possibility of injury to theoperator by being struck by the cam' is eliminated and a more compactfeed control structure as a whole is possible.

From the foregoing description it will be readily seen that I haveproduced such a device as substantially fulfills the objects of theinvention as set forth herein.

While this specification sets forth in detail the present and preferredconstruction of the device, still in practice such deviations from suchdetail may be resorted to as do not form a departure from the spirit ofthe invention, as defined by the appended claims.

Having thus described my invention what I claim as new and useful anddesire to secure by Letters Patent is:

1. A screen unit for a vertical axis ball mill comprising incombination, a skeleton frame extending about the mill and upstandingfrom the base member, sectional screen elements disposed against saidframe and forming a continuous screen structure about the mill, a splitband extending about said continuous screen structure adjacent the topedge thereof and adapted to be clamped about the same, and fingersprojecting inwardly from the top edge of the band across the screenstructure to rest on the skeleton frame whereby to prevent downwarddisplacement of the band when the same is unclamped.

2. A screen unit for a vertical axis ball mill comprising incombination, a skeleton frame extending about the mill and upstandingfrom the base member, said frame including a plurality of upstandingoutwardly fiat and relatively wide arms disposed in spaced relationabout the mill, screen sections disposed against said frame outwardlythereof and forming a continuous screen structure about the mill, theadjacent edges of the screen sections relative to the inner facesthereof overlapping in the direction of flow of material in the mill,each of the overlapping portions being disposed immediately behind oneof the relatively wide upstanding arms whereby to protect saidoverlapping portions from the passing material in the mill, and clampingbands extending about all the screen sections adjacent the top andbottom thereof and removably mounting the screen sections in placeagainst the frame.

J OHN SEROY.

